This invention relates to a failure sensor for a gas detector, for example a Taguchi gas detector.
Gas detectors of the Taguchi type employ a semiconductor element which is heated by an electrical heater coil. At a critical temperature the semiconductor element has a resistance characteristic which exhibits a large change of resistance in the presence of a gas. The resistance of this element falls in value in the presence of gas. The most likely fault condition to arise is (1) failure of the heater, in which case the semiconductor element exhibits a very high resistance; or (2) an open circuit failure of the semiconductor element, which again means that the semiconductor element appears to have a very high resistance.